A large portion of crude oil upon production, contains greater or lesser amounts of salt water in emulsified form. Such emulsions, which occur predominantly as water-in-oil emulsions, must be separated into their phases, since the salt water contained in the emulsion interferes with the further processing of the crude oil, especially with the transporting and distilling of such oil.
The separation of such crude oil emulsions is accomplished by allowing them to stand, by subjecting them to a heat treatment or a centrifuging process, by applying electric fields and by adding demulsifiers.
The crude oil emulsions contained in produced crude oil generally are too stable to be broken by sedimentation, filtration, centrifugation or heating alone. On the other hand, the demulsifiers affect the interfaces of the crude oil emulsions directly and in some cases, bring about a separation of the emulsion even in moderate concentrations.
A large number of demulsifiers has already been proposed. One of the reasons for this, and not the least important, is the fact that different crude oils have different compositions and demulsifiers, which are suitable for breaking emulsions of crude oil originating from one place. may be unsuitable for crude oil emulsions from other extraction sites. The known demulsifiers therefore act to a greater or lesser extent specifically on the individual crude oils.
As demulsifiers, alkyl sulfates and alkyl aryl sulfonates, as well as petroleum sulfonates in the form of the amine salts have already been proposed. Moreover, addition products of ethylene oxide on suitable compounds with active hydrogen atoms, such as alkylphenols, castor oil fatty acids, fatty alcohol, alkylphenol-formaldehyde resins, have been suggested. Appropriate information may be found, for example, in the book "Oberflachenaktive Anlagerungsprodukte des Ethylenoxyds" (Surface Active Addition Products of Ethylene Oxide) by N. Schonfeld, Wissenschaftliche Verlagsgesellschaft mbH. Stuttgart. 1959. page 295.
From the German Patent 1,937,130, the use of polyoxyalkylene-polysiloxane block copolymers is known. These polyoxylakylene-polysiloxane block copolymers have polyoxyalkylene blocks with a molecular weight of 500 to 4,000 and comprise polyoxyethylene and polyoxypropylene blocks in a weight ratio of 40:60 to 100:0. the polysiloxane blocks containing 3 to 50 silicon atoms per block. These block copolymers are liquid to waxy substances, which can be dispersed or dissolved in water. They are therefore added to the water-containing crude oil either as such or in the form of concentrated solutions or dispersions.
Further selected polyoxyalkylene-polysiloxane block copolymers are described in numerous published patent applications or patents. For example, in the published European Patent Application 0,141,585, a process is described for demulsifying oil with the help of polyoxyalkyl-ene-polysioxane block copolymers, the block copolymers corresponding to the general formula ##STR1## In this formula, x and y are numbers from 1 to 200 and the sum of x+y should not exceed 250. R is a copolymeric group, randomly distributed, which corresponds to the formula EQU -R'O(EO)m(PO)nR"
wherein R' is an alkylene group with 3 to 10 carbon atoms. EO is an ethylene oxide group. PO is a propylene oxide group. R" is a hydrogen atom or a hydrocarbon group with not more than 7 carbon atoms. m and n are numbers from 2 to 100 or 2 to 80 and the sum of m +n does not exceed 100.